1. Field of the Invention
The present invention generally relates to an air cleaner and, more particularly, to the air cleaner for use with a motorcycle or the like for substantially purifying air being sucked into an internal combustion engine.
2. Description of the Prior Art
The air cleaner is generally of such a structure as shown in FIG. 6 which illustrates a conventional air cleaner in a side view with a portion cut out. Referring to FIG. 6, the illustrated air cleaner includes a cleaner housing 81, a filter holder 82 disposed within the cleaner housing 81, and an air cleaner element 83 retained by the filter holder 82. The cleaner housing 81 has an air intake port 84 and an air outlet port. An air A introduced into the cleaner housing 81 through the air intake port 84 passes through the cleaner element 83 which serves to remove a dust in the air. The air purified by the cleaner element 83 subsequently enters the engine (not shown) through the air outlet port.
As one of available materials for the cleaner element 83, an urethane foam is largely employed, which is inexpensive and easy to handle and having a high gas permeability. It has, however, been found that the cleaner element 83 made of the urethane foam is so soft as to induce a deformation. Therefore, the cleaner element 83 generally has such a simple sectional shape, for example, a square, round, elliptical or oval sectional shape, when viewed from top, that the cleaner element 83 can be easily held taut. As such, the cleaner element 83 can hardly be formed by a complicated sectional shape enough to allow a volume thereof to increase, when the air cleaner is formed by a complicated shape for avoiding an interference with surrounding parts around the cleaner.
Also, the filter holder 82 is consist of a first holder element 82a for retaining the cleaner element 83, and a second holder element 82b positioned on one side of the first holder element 82a opposite to the cleaner element 83 and connected with the first holder element 82a by means of a fastening element 85 such as, for example, a bolt. When the first and second holder elements 82a and 82b are connected together, a sealing member 86 made of an urethane foam is interposed between the cleaner element 83 and the second holder element 82b to ensure that the air A upstream of the filter element 83 with respect to the direction of flow thereof towards the air outlet port can pass through the filter element 83. However, since in this structure the cleaner element 83 and the first holder element 82a is held in direct contact with the sealing member 86 at one end of the first holder element 82a whose width is narrow, the sealing member 86 made of an urethane foam tends to quickly loose its own resiliency, resulting in decrease of the sealability. Therefore, there is a possibility that the dirt may enter the inside of the filter holder 82 through a gap between the sealing member 86 and the second holder element 82b. Also, since the sealing member 86 is bonded to the cleaner element 83, a replacement of the sealing member 86 requires a replacement of the cleaner element 83 and, therefore, the cleaner element 83 as a whole has a lifetime governed by the lifetime of the sealing member 83.